Universität Stuttgart
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Item Open Access Lateral torsional buckling of glulam beam-columns : axial compression and bending verification(2024) Töpler, Janusch; Kuhlmann, Ulrike; Schänzlin, JörgItem Open Access VisRecall++: analysing and predicting visualisation recallability from gaze behaviour(2024) Wang, Yao; Jiang, Yue; Hu, Zhiming; Ruhdorfer, Constantin; Bâce, Mihai; Bulling, AndreasQuestion answering has recently been proposed as a promising means to assess the recallability of information visualisations. However, prior works are yet to study the link between visually encoding a visualisation in memory and recall performance. To fill this gap, we propose VisRecall++ - a novel 40-participant recallability dataset that contains gaze data on 200 visualisations and five question types, such as identifying the title, and finding extreme values.We measured recallability by asking participants questions after they observed the visualisation for 10 seconds.Our analyses reveal several insights, such as saccade amplitude, number of fixations, and fixation duration significantly differ between high and low recallability groups.Finally, we propose GazeRecallNet - a novel computational method to predict recallability from gaze behaviour that outperforms several baselines on this task.Taken together, our results shed light on assessing recallability from gaze behaviour and inform future work on recallability-based visualisation optimisation.Item Open Access Local laser heat treatment of AlSi10Mg as-built parts produced by Laser Powder Bed Fusion(2024) Kramer, Steffen; Jarwitz, Michael; Schulze, Volker; Zanger, FrederikToday, complex structural components for lightweight applications are frequently manufactured by laser powder bed fusion (PBF-LB), often using aluminum alloys such as AlSi10Mg. However, the application of cyclic load cases can be challenging as PBF-LB produced AlSi10Mg parts typically have low ductility and corresponding brittle failure behavior in the as-built condition. Therefore, this paper presents investigations on the feasibility of a laser heat treatment of PBF-LB produced AlSi10Mg parts to locally increase the ductility and decrease the hardness in critical areas. Potential heat treatment process parameters were derived theoretically based on the temperature fields in the material calculated assuming three-dimensional heat conduction and a moving heat source. PBF-LB produced specimens were then laser heat treated at varying laser power and scan speed. Hardness measurements on metallographic cross sections showed hardness reductions of over 35 % without inducing hydrogen pore growth.Item Open Access Influence of geometry variations during pyrometric temperature measurement in laser material processing(2024) Traunecker, David; Jarwitz, Michael; Michalowski, AndreasItem Open Access SalChartQA: question-driven saliency on information visualisations(2024) Wang, Yao; Wang, Weitian; Abdelhafez, Abdullah; Elfares, Mayar; Hu, Zhiming; Bâce, Mihai; Bulling, AndreasUnderstanding the link between visual attention and user’s needs when visually exploring information visualisations is under-explored due to a lack of large and diverse datasets to facilitate these analyses. To fill this gap, we introduce SalChartQA - a novel crowd-sourced dataset that uses the BubbleView interface as a proxy for human gaze and a question-answering (QA) paradigm to induce different information needs in users. SalChartQA contains 74,340 answers to 6,000 questions on 3,000 visualisations. Informed by our analyses demonstrating the tight correlation between the question and visual saliency, we propose the first computational method to predict question-driven saliency on information visualisations. Our method outperforms state-of-the-art saliency models, improving several metrics, such as the correlation coefficient and the Kullback-Leibler divergence. These results show the importance of information needs for shaping attention behaviour and paving the way for new applications, such as task-driven optimisation of visualisations or explainable AI in chart question-answering.Item Open Access Influence of protection lips on the frictional torque of rotary shaft seals(2024) Olbrich, Christoph; Feldmeth, Simon; Bauer, FrankRotary shaft seals are used to seal rotating machine parts. In most cases one single sealing lip (main lip) contacts the shaft and separates the fluid on one side from the environment on the other side. To prevent the entry of other fluids and or particles, seals with additional protection lips are used (two lips), especially in heavily contaminated environments. When the protection lip contacts the shaft, a vacuum can form between the main lip and the protection lip, leading to increased contact pressure and friction. The increased frictional torque generates more heat and leads to overheating in the contact area between the lip and the shaft. Test runs conducted on a friction torque test bench with various seal configurations confirm that the two lips influence each other. Higher frictional torques and contact temperatures occur, when the volume between the lips isn't vented. This shows the importance of venting.Item Open Access Stream finishing of additively manufactured AlSi10Mg PBF-LB parts: influence on surface quality and fatigue behaviour(2024) Wexel, Helena; Kramer, Steffen; Schubert, Johannes; Schulze, Volker; Zanger, FrederikItem Open Access New insights into the typology of motion in the history of French: evidence from the manner verb lexicon(2024) Piccione, Mariapaola; Rainsford, ThomasOur study aims to investigate the Talmyan typology of motion encoding in the history of French focusing on testing Slobin’s (1997, 2004) hypothesis stating that the proportion of manner verbs is greater in s-framed languages and Schøsler’s (2008) hypothesis stating that the difference between s-framed and v-framed languages is to be found in the use of manner verbs and that the nature of the texts might play a role. Our study is methodologically innovative since it tests these hypotheses against a very large dataset using tailored measures. Our findings show an increase in manner saliency (as defined in Slobin 1997, 2004), contrary to what we would expect. This increase in the proportion of manner verbs might be explained by a more general increase in the overall lexical diversity of motion expression in French. Moreover, our results support Schøsler’s hypothesis, as textual factors affect the use of manner verbs.Item Open Access Comparison of in-process laser drying with furnace and vacuum drying to reduce moisture of AlSi10Mg powder processed in Laser Powder Bed Fusion(2024) Lubkowitz, Victor; Fayner, Leonie; Kramer, Steffen; Schulze, Volker; Zanger, FrederikIn most powder bed-based laser melting systems (PBF-LB), metal powders must be handled without inertization but in an air atmosphere for a short time, increasing the AlSi10Mg powder moisture and reducing the achievable component density. Consequently, different drying methods were investigated. Drying in a furnace with an inert atmosphere, using a vacuum to evaporate the water at low temperatures, and vaporizing moisture layerwise from the spreaded powder with a defocused, low-power laser beam as a further process step of the PBF-LB process. Therefore, four different moisturized powders, which were dried with different settings for the drying methods, are analyzed. All drying methods reduce the moisture content of the powder, with in-process drying being the most effective. Due to the oxide layer growth around the particles during furnace and vacuum drying, the achievable sample density after drying is worse. In-process drying with low energy density is the best option to reach a reduction of hydrogen pores and an increase of density.Item Open Access FIB-SEM tomography for porosity characterization of inkjet printed nanoparticle gold ink(2024) Ruehl, Holger; Reguigui, Hajer; Guenther, Thomas; Zimmermann, AndréInkjet printing is a versatile technology for the manufacturing of electronic devices to be used in various applications [1,2]. Common inks to create conductive layers are suspensions of a solvent with metal nanoparticles such as gold or silver [3]. After the deposition and solidification of an ink on a substrate, the metal nanoparticles are sintered to realize the conductivity of the printed layer. A porous, solid metal matrix remains, whereby the conductivity of the metal layer tends to be dependent on the porosity. To characterize the porosity of inkjet printed conductive layers, focused ion beam-scanning electron microscope (FIB-SEM) tomography is suggested as a potential characterization method in the presented study. For the experiment, a wafer diced silicon substrate with size of 10 x 10 mm² was used, onto which a 1.2 µm thin layer of commercially available nanoparticle gold ink was inkjet printed and then sintered. Subsequently, a four-step procedure for the FIB-SEM tomography-based porosity characterization was performed: 1) FIB preparation of the volume of interest (VOI), 2) serial sectioning including image acquisition, 3) image processing and 4) 3D-reconstruction and porosity analysis. The steps 1) and 2) were conducted using a FIB-SEM dual beam system ZEISS AURIGA 40 (Carl Zeiss Microscopy Deutschland GmbH, Germany). Prior to serial sectioning, a thin platinum layer was FIB induced deposited on top of the inkjet printed gold layer. A cube-shaped VOI with the size 5000 x 6000 x 5000 nm³ was then prepared by FIB milling. The surface to be sectioned was end face polished and a line trench serving as a reference marker for the image processing was milled along the VOI. The prepared VOI prior to FIB sectioning is shown in Figure 1. a). Next, the serial sectioning was conducted. The ion acceleration voltage was set to 30 kV. The aperture current was set to 50 pA, resulting in an ion beam spot size of 12.5 nm, which corresponds to the section slice thickness. No melting and re-sintering of the solid metal structure could be observed during sectioning. SEM images of the revealing surface areas were acquired with 1024 x 768 pixels image resolution and a pixel size of 5.82 nm. Both a secondary electron (SE) detector as well as a backscattered electron (BSE) detector were used for imaging. In total, a 2D stack of 368 SEM images was recorded. For comparison of individual sections, Figure 1. b) and c) show BSE detector images of the cross-sectioned VOI after slice 70 and slice 140. One can clearly see that the size and distribution of sintered metal particles varies along the VOI, forming a porosity network within the solid gold. Since the images acquired with the BSE detector presented a higher contrast and thus, a better distinction between the pores and the metal structure, these images were used for the image processing and final porosity analysis, for which the software AVIZO (Thermo Fisher Scientific Inc., USA) was used. First, the 2D images were aligned to correct for the shifts which occurred during the serial sectioning. Then, a sub-VOI was cropped out to exclude the reference line. The new 3D VOI was of a size of 3026 x 1164 x 2750 nm³, representing a stack of BSE detector images ranging from slice 30 to 250. Noise interference was minimized by applying a Gaussian filter. Afterwards, thresholding was applied as a segmentation technique to differentiate between pores and the solid gold as well as erosion as morphological operation. As a result, a reconstructed 3D model of the pores located in the solid gold was obtained, as shown in Figure 2. a). Using this 3D pore model, the number of pores and their diameters within the VOI could be determined. For the calculation of the pore diameters, each pore was considered to be of a spherical shape. A total of 1509 pores was counted. The pore diameter distribution is shown in the box plot in Figure 2. b). As it can be obtained from Figure 2. b), a pore size of 23 nm represents the lower quartile, while a pore size of 112 nm represents the upper quartile. The median pore size is 44 nm, while the mean is 63 nm, which indicates a trend towards smaller pores surrounded by larger pores. Based on the obtained results, FIB-SEM tomography with subsequent image processing is assessed by the authors to be a proper method to characterize the porosity of inkjet printed conductive layers, which was tested by means of a nanoparticle gold ink.
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